-LRB- CNN -RRB- -- Romanian authorities have arrested three men suspected in last year 's heist in the Netherlands at a Rotterdam art gallery , where paintings ranging from artists like Pablo Picasso to Claude Monet were on display .

Police said the paintings taken had not been recovered but indicated that some of the works might be hidden in an undisclosed location in Romania .

Read more : Picasso , Matisse paintings and more stolen from Netherlands museum

Seven works of `` considerable value '' disappeared in the museum theft , spokeswoman Mariette Maaskant said on Netherlands public radio .

`` Initial investigations show the burglar was well prepared , '' police said in a statement .

Among the paintings taken were Picasso 's `` Tete d'Arlequin , '' Henri Matisse 's `` La Liseuse en Blanc et Jaune , '' and Monet 's `` Waterloo Bridge , London '' and `` Charing Cross Bridge , London , '' Rotterdam police said .

Also taken were Paul Gauguin 's `` Femme devant une fenÃªtre ouverte , dite la Fiancee , '' Meyer de Haan 's `` Autoportrait '' and Lucian Freud 's `` Woman with Eyes Closed . ''

The Kunsthal museum 's alarm system went off shortly after 3 a.m. local time on a mid-October morning , alerting the exhibition hall 's private security detail . When security staffers arrived by car , they saw that the paintings were missing , Rotterdam police spokesman Roland Ekkers said .

The works belong to a private collection that is being shown for the first time to the public , according to a Kunsthal statement .

The Triton Collection has taken 20 years to assemble and includes more than 150 works of modern art from the `` late nineteenth century to the present day . '' It spans art movements from impressionism and expressionism to cubism and constructivism .

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Police say the paintings are not yet recovered

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They indicated some might be hidden in an undisclosed location in Romania

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Seven works of `` considerable value '' disappeared in the museum theft